Tach no worky-worky

So, I am assuming many have crossed this path before, so the answer is probably obvious. I did some searching and found some comments from Andy (Eliteman76) from some time ago.

my 75 Sport is now running and driving. The ignition is new - removed the brain box, distributor and coil and replaced with a Mallory Unilite distributor and MSD Blaster coil. It works obviously but the tach no longer works. I believe (but need to verify) I tapped the coil + and ignition module + correctly off factory wiring to the new coil + and distributor + respectively.

However the tach no longer works. I thought for sure I tapped the correct wires because I was trying to ensure I was using the resistance wire for the coil as we should always try and do unless we intend to wire up an external ballast resistor. I replaced the tach with another from another cluster. The original and replacement tachs were known good units.

Is it something about the coil and/or distributor causing this? They are pretty vanilla parts.

Do I just have it wired up wrong somehow? That is a real possibility. I am leaving for a week, hence no ability to troubleshoot for a while (I am driving the car to Spokane for a week), but can get on it when I get back.

Other thought - Should I just run a new coil power wire from my ignition switched relay source I created and go through an external ballast resistor and include the coil in the run? It almost makes more sense to just bypass as much of the factory wiring as possible, as old and crappy as it is.

I think with the 2 wire tac you have to get the adopter from MSD.

Edited by dave302 - 02-August-2014 at 2:49AM

Dave thank you very much for the links. You are five thousand times better than the search engine here!

It almost seems like sending my tach ( and other gauges) into Rocketman for modification may be best.

Dave, I thought I remember seeing someone sending their tach out to be updated?

I am running into the same issues with the tach not working with a 1-wire HEI. I thought about having the original reworked and updated.

carguy47 wrote: Dave, I thought I remember seeing someone sending their tach out to be updated? I am running into the same issues with the tach not working with a 1-wire HEI. I thought about having the original reworked and updated.

are you referring to the gm style 1 wire HEI? if so, that's what i'm running on my car, and i have the factory two wire tach hooked up and working.

carguy47 wrote: Dave, I thought i remember someone sending their tach out to be updated?

Edited by dave302 - 03-August-2014 at 4:13AM

Are newer tach typically voltage driven now?

Are these new tachometer repairs/conversions voltage driven as well?

http://www.tachman.com/index.htm

Who is the other guy Paul recommended for Cougar, Mustang, Ford tachometer conversions?  
I can't seem to find it now...

Reason I ask; I was about to buy the MSD tach adapter but realized that I probably wont need it if I get my tachometer converted/fixed by tachman.com

My tach is bouncing and jumping around.  Needs to be fixed/replaced.  I've been looking for 7k/8k options without any luck so I'm now looking at simply getting it upgraded by tachman.



Edited by BackInBlack - 13-June-2017 at 10:41AM

Thanks...that answers my question!

John,